Distance adjusted pneumatic control system



Jan. 19, 1954 L. GESS DISTANCE ADJUSTED PNEUMATIC CONTROL SYSTEM Filed Sept. 11, 1948 8 Sheets-Sheet 1 INVENTOR. LOUIS GEISS BY MM 4 ATTORNEY.

Jan. 19, 1954 L sass DISTANCE ADJUSTED PNEUMATIC CONTROL SYSTEM Filed Sept. 11, 1948 -8 Sheets-Sheet 2 INVENTOR. LOUIS GESS flaw ATTORNEY.

Jan. 19, 1954 GESS DISTANCE ADJUSTED PNEUMATIC CQNTROL $YSTEM Filed Sept. 11, 1948' 8 Sheets-Sheet 3 III III"! INVENTOR LQUIS GESS .BY fi/ I ATTORNEY.

Jan. 19, 1954v 595 2,666,585

DISTANCE ADJUSTED PNEUMATIC CONTROL SYSTEM Filed Sept. 11, 1948 8 Sh'bets-Sheet 4 FIG. 5

' INVENTOR. T H 'LOUIS sass ATTORNEY L. GESS Jan. 19, 1954 DISTANCE ADJUSTED PNEUMATIC CGNTROL YSTEM 8 Sheets-Sheet 5 Filed Sept. 11, 1948 INVENTO. LQUIS GESS ATTORNEY.

Jan. 19, 1954 L. sass DISTANCE ADJUSTED PNEUMATIC CONTROL SYSTEM Filed Sept. 11, 1948 8 Sheets-Sheet 6 FIG. 8

FIG.9

l l'l- INVEN TOR. LOUIS GESS fl VM ATTORNEY Jan. 19,1954

L. GESS. DISTANCE ADJUSTED PNEQUMATIC CONTROL SYSTEM Filed Sept. 11, 1948 8 Sheets-Sheet '7 wmw Jan. 19, 1954 L. GESS DISTANCE ADJUSTED PNEUMATIC CONTROL SYSTEM Filed Sept. 11,1948" I 8 Sheets-Sheet 8 7 4 O -111 O 3 6 3 o u M 3 M 3 p 4 m 3 r 6 3 I 3 3 I t 4 8 3 M. G 8 M O Y 4 F a a .v 0 0 \CMK 3 1w 7 N A L b Q91 PHJ H m 7 3 AU 3 2 D s u 3 0 0 A. 3 m 2 3 M v u .n ,s 3 u 3 2 5 3 2 3 STEPS I l INVENTOR. LOUIS GESS ATORNEY. v

Patented Jan. 19,

DISTANCE ADJUSTED PNEUMATIC CONTROL SYSTEM Louis Gess, Je'nki'ntovi' n, Pa., assignor, by mesne assignments, to lvilinneap'olis-Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application September 11, 1948, SerialNo. 48,856

In many modern industrial processes it-is-undesirable and inse'mfe cases impossible for the operator.or-personhavingcharge of the process to be close'to it. This'lS for the reason that such processes are-so hot,di'rty, noisy or dangerous that it is inadvisable for a'hu'man being to be at'their immediate vicinity.

It is 'atheoretical ideal that processes be made completely automatic. Obviously this-theoretical ideal can not be realized completely in actual practice because in'the beginning the process must be started u'p' and must, eventually, be shut down. Therefore it is nece'ssar'y that means be provided to controlsuch'processes from a remote point,' hereinafter referredto as the control 10- cation. In erder to -exercise the control of such aprocesa-thereinust-be (1) a final control element, such as a valve, "controlling one process variable;- (2) a measuring element responsive to the variable undrcontrol; and (3) a controller,

whereby the measuringelement actuates the final control element. --Such"a controller usually in volves aseparatesource-of power and a relay .wherebythe measuring element, which is sensirecording the control of many variable functions such as temperature, pressureyfiow or liquid level.

6 Claims. (Clf236 -'1) Apanel board on whichthe various controlmeans are arranged islocated atthe control room.

It is an object of 'this iinvention to provide at such acontrol location an'indicator or recorder to inform'the operator that the control operations whichihehasinitiated from the control location have been transmittedit'o the various final-control elements located throughout the plant and that the consequent :operations of these final control elements have actually affected the process under control in the desired-manner.

- Afurtherob'ject "of thisinventionis to'provide air-operated means ontrollingthe final con-1 2 tions of the final control elements to the control location. The advantages of air-operation for these purposes are well known. Foremost among these advantagesis the removal of the explosion hazards where explosive gases or fluids are present. Additional advantages are the inherent stability,.accuracy and flexibility of air operation.

Yet another object of this invention is to providea control system having manually operable elements at a control location from which a controller located adjacent the final control apparatus can be controlled by hand so that the operations of the controller vary the final control element as quickly as possible with a minimum of lag or delay.

A still further object of this invention is to provide a control system having an indicator or recorder at the control location and under the control of the controller so as to indicate the movements of the controller and having a measuring instrument located adjacent the process variable under control and arranged to be sensitive to changes in this process variable.

The various features of novelty which characterize this invention are pointed out with particularity in the claims annexed to and forming a part of thisspecification. For a better understanding of the invention, however, its advantages and spe-- cific objects obtained with its use, reference should be had to the accompanying drawings and descriptive matter in which is illustrated and described a preferred embodiment of the invention.

Of the drawings:

v Fig. 1 is a front elevation of the transmitter. and the adjacent indicator.

Fig. 2 is a diagrammatic or schematic view in projection showing the transmitter with parts in cross section.

Fig. 3 is a side elevation of the transmitter and its associated indicator with partsin vertical cross section.

Fig. 4 is a re'ar elevation of the transmitter and indicator With the rear cover removed'as viewed from the line 4--'4 of Fig. 3.

I Fig. 5 is a front elevation of the controller with the front cover removed showing'p'arts in vertical cross section.

- Fig.6 is a diagrammatic or schematic showing of a complete pneumatic transmitting, controlling and indicating system according to this invention. Figs. 7 through 9 are diagrammatic or schematic showings of modifications.

Fig; '10 is a diagrammatic or schematic showing of yet another modification.

- Fi'gfll is a diagrammatic tabulationsh owing Fig. 1 shows the front or face of the transmitter which is located at any convenient control station, such as the panel board. A handle or an operating knob I is rotatably mounted in the panel board beneath an indicator 2 having a pointer 3 moving over a dial 4. Knob I bears an arrowshaped marking on it cooperating with a stationary curved scale which may be logarithmic (as shown) or of any desired spacing toindicate the position to which the knob I is set. Fig, 2 shows that handle I turns a shaft 5 connected to gearing 6 which, in turn, rotates a bell crank lever I about its pivot 8 and thus moves a link 9. Attached at the far end of link 9 is a lever I0 fast on a shaft II to which is also secured a second lever I2 bearing a flapper-operating pin I3. Pin I3 is movable into and out of engagement with a flapper I4 which is pivotally movable about a stationary pivot I 5. Flapper I4 is stressed by a spring towards engagement with a nozzle I6. Nozzle I6 forms the control of a pilot valve of a well known commercial type which includes an air inlet pipe I! which admits air to a forked channel. One fork or branch of the channel leads through a filter I8 and an adjustable restriction I9 to a pipe ending at nozzle It and to a branch pipe 2| leading to casing 22 which contains outer bellows 23. Secured to bellows 23 is one end of a hollow exhaust pipe 24 which is also secured to the inner bellows 25 which seals the exhaust pipe to the pilot valve or relay casing 26. The lower end of exhaust pipe 24 is sealed by a second flapper 2'! when the exhaust pipe 24 engages the flapper 27. Flapper 27 also controls the main flow of air through the nozzle 28. Exhaust pipe 29 leads to the receiver or other device controlled by the pilot valve or relay. Feedback pipe 30 leads from the off-take side of the flapper-chamber and communicates with bellows casing 3I containing a bellows 32 stressed by a spring 33 and having its motion limited in one direction by a cylindrical stop 34. Motion of bellows 32 is transmitted to a differential, one input of which is provided by the manually caused movement of knob I and the other input of which is formed of the resetting movement of bellows 32. Bellows 32 moves a link 35 at the end of which is formed a pin 36 slidable in a slot 3?. A bell crank lever 38 is pivotally mounted on a stationary pivot 39 and contains in it an opening Gil through which the shaft II passes.

FIGS. 3 AND 4 Figs. 3 and 4 show this manually operated transmitter in greater detail. The knob or handle I is rotatably mounted in the panel so that its front face is substantially flush with the front face of the panel. The shaft 5 is stressed by a spring M which tends to take up any back lash which there may be in the gearing 6. The bell crank lever I is biased for counterclockwise rotation'by a spring 42 one end 43 of which engages the bell crank lever 'I and which is fastened to the instrument casing at its opposite end 44. Bell crank lever I, by means of 1ink'9 and lever I II, turns shaft II and pin I3 carried thereby. Spring 45 has one end 46 fast to the instrument casing and stresses at its other end 41 against the bell crank lever 38, tending to hold the bell crank lever 38 against the pin 36 which is located in the slot 31 forming a part of the lever 38. The air inlet I'I communicates with the pipe 20 which leads to the nozzle I6 while the air outlet pipe 29 communicates with the pipe 30 which leads to the casing 3| which contains the reset bellows.

Operation of Figs. 3 and 4 The operation of the manually operated pneumatic transmitter will be readily understood by referring to Fig. 2. When the manually operated transmitter is turned, it operates the receiver which is connected to the air outlet pipe 29 so as to adjust the set point or control point of a controller located at a remote place. Turning knob I in one direction'or the other operates the flapper pin I3 through the mechanical linkage formed by shaft 5, gearing 6, bell crank lever I, link 9, lever IIJ, shaft II, and lever I2. Movement of pin I3 in engagement with flapper I4 turns the flapper I4 under the stress of its actuating spring about the flapper pivot I 5. The movement of flapper I4 relative to nozzle I6 varies the air pressure applied to bellows 23 and causes consequent movement of exhaust pipe 24 so that either air is exhausted from the pilot valve or the flapper 2'! is moved away from nozzle 28 to admit additional air to the pilot valve chamber. When suii'icient air is exhausted from or admitted to the pilot valve, the bellows 25 contracts or expands and the flapper 2! closes off the exhaust pipe 24 and the inlet nozzle 28. The air controlled by the pilot valve fiows through the outlet pipe 29 to the receiver connected to the opposite end of pipe 29. The controlled air within the pilot valve is also fed through pipe 30 to the bellows casing 3I wherein it causes consequent movement of bellows 32. The movement of bellows 32 (due to any difference existing between the air pressure in the bellows casing 3i and the stress of spring 33) is transmitted by the link or bellows rod 35 to the lever 38. Rotation of lever 38 in one direction or the other rotates flapper pin I 3 in the opposite direction to which it has been set by knob I and thus resets the flapper I4 so as to control the air pressure within the bellows casing 22 at the new value desired.

FIG. 5

Fig. 5 shows the details of a controller which is located adjacent the valve or other final control element. This controller may be of the type shown in U. S. Patent 2,125,081, granted July 26, 1938. This controller contains a measuring element, which is shown as being a thermometer formed by a spiral or Bourdon tubing 48 actuated by liquid or vapor pressure from a suitable bulb 49 located at the point, whose temperature it is desired to measure. However, instead of a measuring element for temperature, a measuring element for pressure, flow, or liquid level may be employed. The movement of' the measuring element 48 forms one input of a differential, generally indicated at 50. 'The other input of differential 50 is provided ,by an air-operated receiver, generally indicated at 5|, and connected to the manually operated transmitter by a pipe 29. Receiver 5| is formed bya bellows casing 52 con taining a bellows 53 which is matched to or interchangeable with the bellows 32 of the manually operated transmitter. Bellows 53 is stressed by a spring 54 and has its movement in the direction in which it isoperated by the air within the bellows casing 5| limited by a cylindrical stop 55.

Be lo s 53 ve ga eso e d o a l w ro :01. link lit-whose. opposite end has-pivotal engagement with a lever system, generally indicated at 57. The out-put of lever-system 51 is transmitted by link 58' which forms one input of thedifierential, generally indicated at 50.

'The position of measuring element 43 is also fedto asecond transmitter, generally indicated at 59,-by means of a link 60 which controls the setting of the pin 6! operating the flapper 82 with relation to the nozzle 63. The transmitter variable being measured at that instant by the measuring element of the controller at the remote location. Control of the final control element, such as a valve operated by an air-driven diaphragm motor or the like, is exercised by a pilot valve, or relay, generally indicated at 68, having an air inlet pipe 69 and an air off-take to the valve or other final control element. This controller is a well known commercial type and has an adjustable throttling range and an automatic reset. The pilot valve 68 is controlled by means of a nozzle H which is responsive to the flapper I2 controlled in turn by a flapper-actuatingpin 13 mounted on a three-armed lever l4 pivotedat 7B, which is actuated from the difierential 59 by means of a control link 15. a

Movements of the measuring element 48 are transmitted by a spring arm Tl to the arm 18 of a three-armed lever mounted on a stationary pivot 19. Arm 8 0 ofthisthree-armed lever is connected to one end of link (ill. The third arm SI: of this lever haspivotallyconnected to its free enda diiierential'link 82 which is pivotally se.-

cured at its opposite end to one end of a floating lever '83. The opposite end 84 of lever 83 is car- .ried by one. arm 85 of a second three-armed lever pivotally mounted on a stationary pivot 86.

The control link has pivotal engagement with I the floating lever 83 at point 89A, intermediate the ends of the floating lever 83. Thus the cut put of the differential '50 is connected by means of control .link 55 with one arm of the three-' armed. lever M that is pivotedat l6. This'lever hasa pin 13 on it which serves to move flapper 32 against a suitable biasing force away from or to permit the flapper tomove toward nozzle H to throttle the. flow of air through this nozzle. The nozzle 1!, along with a chamber formed in the pilot valve 68, is supplied with air from pipe 59. restriction isformedin the supply pipe to the nozzle Ti and the chamber so that air i supplied thereto'at aslowerrate.

As the "pressure in thelchamber is varied, a follow 'up movement is given-to the flapper '72. by means of the actionof a rod 88 anda projection 85, thereon upon'fa first lever 9.0 that pivoted atj'tii, a pin 22 and a second. lever 33. that is pivoteii. at; 9.3a; vlvliich second lever supports, the

three-armed lever 14:by 1ne;ans of pivot 76. This pin 92 is attached to a supporting arm 94 and may be moved'upwardly and downwardly between levers 9i} and 93' to changethe throttling range of "the instrument. Asthe lever 93 is'moved, the

flapper is shifted in a direction opposite to its 7 originalmovement in order to bring the instrument back to equilibrium. This second or follow up movement is followed by a third compensating or reset movement. As pressure of the liquid in the. chambers between bellows '95 and 9e and bellows Ell and98 is equalized through the connection 99, the speed at which this reset motion can take place isdepe'ndent upon the adjustment of the'restriction I00.

The total amount of follow-up movementthat can be obtained, maybe limited by the amount of movement that can be imparted to the lever 93. To this end the lever'93 is formed with a pair of fingers Hll which extend on either side of a shaft 102.

Operation of Fig. 5

In theoperation, of the instrument, if for examp1e,'the temperature being measured has been increased, the pen88A will be moved in a counterclockwise direction outwardly across its chart.

This same movement will cause the left-hand Y direction. Sucha movement will move the pin 73 to the left so that the flapper 12 will be moved away from the nozzle 1|, permitting more air to escape vfrom this nozzle with a consequent decrease in pressure in the chamber of the pilot valve '68. The. escape of air from the chamber of the pilot valve 88, will also cause a reduction of pressure in the chamber surrounding the bellows es thereby ermitting the rod 83 with its projection 89 to move to the right. The. levers 90 and 93 and the pin 92 will therefore cause a movement of the pivot point 16 and lever 14 to the right so that flapper '12 will be given a follow-up movement towardthe nozzle, II. If the temperature being measured deviates a considerable amount from the control point of the instrument; the lever 93 will be forced to move in a clockwise direction until the lower oneof the members Hll engages with rod I02 to stop further movement'of this lever. Thereafter, the control instrument operation in that direction will be as an onl-off instrument, since no further follow-upcan be obtained. r

In like manner, a decrease in the temperature being measured will causea reverse operation to that above described. so that .an increase in a pressure is obtained throughout the system with the lever 93 moving in a counterclockwise direction to an extent limited .byengagement between the upper member ml and the shaft use. It will therefore be seen that an air pressure corresponding to the temperature being measured will be set-upinthgchamber of the pilot valve 63 and this pressurewill be varied with the changes in temperaturewithin reasonable limits on either side of the control point. When the temperature changes-beyond these limits,- .however, further follow-up movement can not be, obtained dueto engagement of one of the members I0l with the shaft" I02. Thereafter, the pressure in the chamber in the pilot relay 8%! will go immediately to one of its limits. The amount of deviation from the control point, which is permitted the temperature prior to the time that the members W engage the el ci .49 1??? b j e i Q -FIG.6

Fig. 6 shows in a diagrammatic or schematic form, a complete transmission system. The transmitter and its associated indicator (shown in detail in Figs. 3 and 4) are located at the left within the dotted and dashed lines Z, while the controller (shown in detail in Fig. 5) is indicated at the right within the dotted and dashed lines Y. Fig. 6 shows that the knob I controls the operation of flapper I4 cooperating with nozzle Iii. Inlet air from pipe I'I branches and passes through restriction I9 and pipe 20 to nozzle I6 and also passes to the inlet nozzle 28 of the pilot valve or relay 26. Flapper 21 controls the'admission of air through inlet nozzle 28 and the escape of air through exhaust pipe 24. Exhaust pipe 24 is operated by bellows 23 within casing 22 in response to the air pressure maintained at nozzle I6 and transmitted through pipes 20 and 2|.

Outlet pipe 29 conducts air from the pilot valve or relay 26 to the receiver, generally indicated at SI, and having bellows 53 within casing 52. The controlled air from pilot valve 26 is fed back through pipe 30 to bellows casing 3I where it actuates bellows 32 to reposition flapper I4 by means of the difierential shown in detail in Fig. 2. 1

Referring now to the controller within th dotted lines Y, it will be seen that the measuring element 48 feeds into one end of the difierential, generally indicated at 50. The opposite end of the differential is fed from the receiver 5| by the linkage shown in detail on the right-hand of Fig. 5. The motions of measuring element 48 are fed directly to flapper 62 which cooperates with nozzle 63 forming part of the transmitter, generally indicated at 59. This transmitter comprises a pilot valve 65 to which air is fed from the pipe 65. This inlet air passes through restriction I05 to pipe 64 which terminates in nozzle 63. Pipe 64 also contains a branch I06 communicating with a bellows casing IO'I in which are housed bellows I08. Pilot valve 65 has a flapper I09 controlling an exhaust pipe I I actuated by bellows I08 and inlet nozzle II I forming the end of inlet pipe 66. Off-take pipe 61 leads back to the indicator 2 located at the control station adjacent the handle I. Pipe 61 also communicates with pipe H2 which leads back to bellows casing H3 containing bellows H4 which feed into a differential so as to give repositioning movement to flapper 62.. The movements of measuring instrument 48 and of the receiver which moves the control point or set point of the controller, control the actuation of the final control element, such as valve H5, by means of a pilot relay 63 to which air is lead through an inlet pipe 59 and from which air escapes through a pipe III. Pipe III also communicates with the throttling and reset mechanism explained in detail in connection with Fig. 5. This mechanism serves to reset flapper 12 by means of pin 89. Inlet air from pipe 69 passes through restriction HE and through pipe III to nozzle 'II. Pipe II'I contains a branch H8 communicating with a bellows casing H9 containing bellows I20. The full flow of air from pipe 69 passes through inlet nozzle I2I, controlled by a flapper I22, which also controls the exhaust pipe I23 which is moved by bellows I20.

Operation of Fig. 6

When itis desiredto adjust the setting of the controllerv actuating the final control element H5, knob'i is turned so as to adjust flapper I4 relative to nozzle'I8.- This variesthe air pressure in bellows casing 22 and causes exhaust pipe 24 to either exhaust air from pilot relay 26 or to move flapper 21 to admit additional air to pilot relay 26 through nozzle 28. This change in air pressure in pilot relay 26 is transmitted through pipes--29 and 30 to bellows casing 3I where it causes bellows 32 toreposition flapper I4 to a value corresponding to the pressure thus manually established by turning handle I. The output pressure through pipe 29 is also transmitted to receiver 5| where it actuates bellows 53 and through a differential 5D actuates the floating lever 83 and the pivoted lever I4 so as to adjust flapper I2 relative to nozzle II. A variation in the flow of air throughout nozzle II varies the pressure within bellows casing H9 and thus causes the bellows I20 to move the exhaust pipe I23to either exhaust air from the pilot relay 68 or to move flapper I22 to admit air to the pilot relay -68 through the inlet nozzle I2I. This changed air pressure in the pilot relay 68 is transmitted through outlet pipe III to the diaphragm or other air-operated motor which drives the final control element H5. The air pressure which is applied through pipe I5 to the final control element I I5 is also fed back through pipe I6 to the throttling and resetting mechanism where it moves the pin 89 and thereby affects a throttling or resetting movement of flapper 12 as has already been described.

It will thus be seen that this transmission system affords means whereby a final control element H5 may be operated either manually by means of knob I from a control location which may be at any convenient point or may be operated from the measuring instrument 48 which is located close to the final control element H5 so that the controller is close to the final control element and actuates it without appreciable delay or lag.

' FIG. 7

Fig. 7 shows a transmission system very similar in its construction and operation to that shown in Fig. 6. The principal difference is that in place of the indicator 2 of Fig. 6, there is a recorder, generally indicated at HGA. This recorder includes a receiver having a casing H6 enclosing a bellows I31. Bellows H1 moves a pen arm H8, bearing on it a pen H9, over a suitable chart I28. The indicator 2 instead of indicating the movements of the measuring instrument 48, is connected by pipe 61A to the motor for the final control element H5. The manually operable transmitter and the controller, whose set point is controlled by this transmitter and which is responsive to the measuring element 48, have the same elements to which the same reference characters have been applied as in Fig. 6, and operates in the same way.

FIG. 8

Fig. 8 shows a further modification in which a plurality of final control elements I2I, I22 and I23 can be actuated by manua1 control handles, each mounted on a small panel and located at the control board or other central location from which the controller of an entire industrial processing plant is exercised. There is also provided at this control station, a multi-pen recorder which records the movements of each of the final control elements. The manually operable handles I24, I25, and I26 are the operating mechanisms of pneumatic transmitters which 9 operate-pneumaticreceivers I21, I28,- and' I29; respectively."These receivers I21, I28, and I29 :feedinto-differentials I30, I31, and I32, respectively, as well'as operating set point-indicators 133, I30, and I35,'respective1y. Adjacent the finalcontrol elements I21, I22, and I23:are controllers having measuring elements I36, I31, and 138, respectively. These :measuring elements also feed into the differentials I30, I3I, and I32, and likewise operate indicators I39, I40, and I4I and also operate pneumatic transmitters I42, 443, and I 44, respectively. These pneumatic transmitters I c2, I43, and I44 are connected to lpneumatic receivers I45, I46, and I41, respectively. These receivers actuate pen arms I48, 149, and I50, respectively. The differentials I30,

HI, and I32 control flappers cooperating with nozzles II, I52, and (53; respectively. These nozzles form parts of pilot valves I54, I55, and I58 which have, respectively, off-take pipes I51,

I58, and I59 leading to the motonfor the final control elements I 2|, I22, and I23, respectively.

The off-take pipes I51, I58, and l59- also lead to throttling and reset mechanisms I60, SI, and I 62, respectively, whose-action has been'explained in the description of Fig. 5'.

The modification of Fig. 8 thus shows howa number of final controlelements-can be actuated from a single control station under the control of a single operator and the variations sensed by measuring elements adjacent these'flnal control elements can be recorded on a single multichart at the control location.

Fig. 9. shows a pneumatic transmission system which provides means for setting the indexof a controller located at a remote point and for also providing a record of' the control point ofthat instrument at the control station. At the control station, there is located within the lines X an instrument having the outwardappearance of a controller. equipped with a pen I633, an index I64 and a setting knob I65 for the index. The

manually operable setting knob I65 feeds into a branches apipe I19 leading to bellows casing I80in which are housed bellows I8I which feed into a difierential so as to operate or reposition the flapper I661 The outlet pipe I18leads to'an air-operated receiver 5| forming part or a, coirtroller located within the dotted and dashed lines Y and corresponding to the'-'controllers' shown in Figs. 6 and 7. I When the operator turns the manually operable handle [65, he does not directly change'the set point ofthe" instrument at the control station but instead sets'in motion pneumatic transmission, ap aratus chanteuse a pressure to the remotely installed'c'ontroller within the lines Y where 'th'eindei is positioned automatically. In order to"provide- Irap d'fan'd accurate setting =of the juice; on the co ntrellerf use is made -:;ofpneiimatic-tral amitter units;

This eliminates the inching operation whichis necessary when a pressure regulator-is employed for; this purpose. Furthermore, the use-off such a transmission system results in maintaining position of the; indexwithout-deviation or drift.-

.Moreover, the consumption of air'is reduced to:

an absolute minimum.

r This modification is a controller by means of which a final control element is controlled either manually-or automatically and in which there provided means for-adjusting from a control 10- cation the set point of a primary controller'or-of a: secondarycontroller, which are the. means for automatically controlling the final control element.

Filtered air supply 200 is controlled by -a first manually operable air-pressure regulator 201 which is mounted on a panel similar to the panel shown in Fig; 1. This panel is at a control location which may conveniently be the control room orother place from which arr-entire in dustrial process plant is controlled; The various fina1 control elements are located at various locations throughout the plant remote from the control location. From the pressure regulator-- 2'0I a pipe- 202- leads to a switching valve 203'.

The switching valve 203 is manually operable Theform illustrated diagrammatically in Figs. 10 and and may be of various structural forms;

11 is a cylindrical casing having seven ports through it which are indicated in thedrawings by the reference characters A, B, C, D, EQF, and

- G. The movable element ofthevalve is a plughaving channels through it which connect t-he various portsA-G to one another in sequence of five steps shown inFig. 11.

The pipe 202 connects with the port A. The port E connects withthe air-operated motor 204? for the final control element 205 which is locatedat some point in'theplant or process controlling apparatus remote from the control location. Port l3! is also directly connected to air-pressure-operated indicator 206 located; at.

the control panel so as to indicate the pressure applied to-motor 204'. The same source of filteredair supply 200 or a second source of airsupply 201 communicates with a second manually operable air-pressure regulator 208 from which an outlet pipe 209 leads to the valve portC. Valveport- D is connected by means of pipe 2! with a pair of'relatively movable parts constituting anair-operated receiver 2. Receiver 2II forms part of a secondary controller, generallyindicated' at. 2I2, which is of the type disclosed in detail in Fig. 5. The parts of controller 212. are located within a controller casing 2I3. Anozzl e 2I4 is controlled by a flapper valve 2I5; A measuring element 2I 6 forms one input to a .differential linkage 2-I "I including a movable pivot. A pilot "valve "has a motor 222 operated in re; spouse to the fl'ow' of air through nozzle 25.4. Filtered air supply 219 leads to nozzle 220 and to restriction 22I in the pipe leading to nozzle 2I4. Motor 222 operates exhaust pipe 223 by means of a mechanical linkage. Pilotyalyeila has a flapper 224 controlling nozzle 220 and ex haust valve 223 The, outlet pipe 225 from pilot relay-2 I 8 branches. Pipe 2261'eads to a res t-device221 which has a mechanical linlgas22-to ii 12 b? d f e ent al 2' w sr 1.! .lwse mec lianical linkage 230 with. arm 23I of differential 2I1. The opposite end'of arm 2,3.I is

connected to measuring instrument 2I6. The

output of differential 211 isthe'flapperpin 2327 which actuates flapper 215. r

The other branch of pipe 225 is pipe 233 which 240 from which one pipe leads through an air-' operated motor 241 and a branch pipe 242 leads to a nozzle 243 controlled by a flapper 244. The output air from relay valve 236 branches. portion passes through a pipe 245 to an air operated motor 246 which constitutes a repositioning device having a mechanical connection 241 to one end of a differential arm 248 the op-' posite end of which is connected by means of a mechanical linkage 249 to measuring instrument 2 I 6 through difierentia1 211, if desired. The output of differential 248 is the flapper actuating pin 250. i

The other portion of'the output air from relay 236 passes through pipe 251 to an air-operated receiver 252 forming part of a recorder generally indicated at 253. A pivotally mounted pointer or pen arm 254 is pivoted within a recorder casing so as to pass over a chart 255 and record a mark-" ing on the chart.

A second controller similar to that shown in Fig. 6 and to that generally indicated at 212 is generally indicated at 256. This controller has One the filtered air supply 251 which branches. portion of this air is supplied to a nozzle 258 of a pilot valve or relay 259 having an exhaust valve 260 which, together with a nozzle 258, is controlled by a flapper 261. Another portion of the air from inlet 251 passes through restriction 262' to nozzle 2 63 controlled by flapper 264 and to motor 265 which operates relay valve 259 by means of the exhaust port 260. One portion of the outlet air from relay 259 passes through pipe 266 to port B of switch valve 203 while the other portion of the outlet air from pilot valve 259 passes through pipe 261 to reset device 268.

From port F of switch valve 203, pipe 269 passes through an air-operated receiver 210 which is connected to one end-of a lever 212 which forms part of a differential generally indicatedat 211. A measuring instrument 213 is connected to the opposite end of lever 212.

The output 214 of lever 212 connects to one end of a second differential lever 215 whose opposite end is driven by a mechanical connection 216 from reset device 268. The output of differential 211 is formed by flapper pin 211; mechanical connection 218 leads from measuring instrument 213, -to-difierential=211, if desired, to one end of a differential lever 219 whose" output is formed by flapper pin 280. "Pilot valve 281 has a nozzle 282, connected to filtered air gigply 251, an exhaust valve 283, and-a flappe Air from supply 251 also passes through restriction 285 to an air-operated-motor 286 hav-' mg a mechanical connection-281 with exhaust valve 283 and to nozzle 288' controlledby flapper 289.

The outlet air from pilot relay 281 branches.

one portion passes up through pipe 290 toan air-operated motor 291, constituting a repositioning device, having a mecha ical Connection Pipe 234 parallels this end One 12 292 to the opposite end or; differential--lever 219.- The other portion of-the outlet air from -pilot re1ay281passes through pipe 293 to'an air-operated motor*294 having a mechanical connection 295 with a second indicator or pen arm 296 pivotally mounted within the recorder and movable in response-to movements of'motor 294 so as to mark records'on chart 255.

FIG. 11

This figure is a diagrammatic or schematic showing of the connections between the various ports of the switching valve 203 in each of the various, successive steps "by whichthis controller performs various operations. When it is desired to start up-the process under the control of the final control element 205, the switching valve is operated into the position in which it is shown in Fig. 11, step 1, in which the valve ports A and E- are connected. Air thus passes from the inlet 200 throughthe first manuallyoperable air-pressure regulator 201, pipe 202, the switching valve ports A and E to the motor 204, which operates the final control element 205, and also to the first air-pressure-operated indicator 206, which indicates the instantaneous value of the air pressure applied to the motor 204 and consequently the position of the final control element 205. The next step 2 is to adjust the set point of the secondary controller 212 so that it can assume control of the final control element 205 and maintain the final control element at the position to which it has been set by the manually operable pressure regulator 201. In order to do this, the switching valve 203 is turned into' the positionin which it is shown in Fig. ll, step 2. In this position, ports A and E of switching valve 203 remain connected so that the manually' operable pressure regulator 201 can adjustthe valve-operating motor 204. At the same time; ports C and D of switching valve 203 are con-- nected: Air enters from'supply' 201 and passes through second manually operable air-pressure regulator 208, pipe 209, valve ports C and D, pipe 210, to receiver 211;"Second regulator-208 can be manually" adjusted so that movement of receiver 2| 1' moves linkage 230, and difierential 211 so as to adjust the'position of flapper 215 relativeto nozzle 214"and thereby control the flow of' air through second pilot-or relay valve 218. Thecontrol flowof outlet air from second pilot or relay-218 passes'through pipe 233 to second air-pressuremperated"indicator 235 which is locatedat the control location adjacent the first indicator 206. This permits'the air pressure applied to'themotor 204' to-becompared readily with the air-pressure applied to the controller 212; When these two pressures are equal or approximately equal, step'3can be taken. This step consists in taking the control of the final control element 205 away from the flrst manually operableair-pressure regulator 201 and connecting- -the motor -204- "under theautomatic control of thesecondary controller 212. Fig-11, step 3, shows that this is-done'by shutting off the connection between ports A and E and making a connectionbetween ports G and E of switching valve 203. The-motor 204' is thus connected under the control of theameasuring instrument 216 of 1 the secondary-controller 212. If it is desired to adjust-the set point of thesecondary controller- 2 12automaticallyinstead of manually, .by means of the-second manually operable air-pressureregulator 208, the switching valve 203 is next turned into the-position inwhich it is shown in v 13 Fig. listen 4. m th s position the connection between ports G and remains made, however, and connection is made between ports c and F. Air news from the supp y 201 through the'sfecnd manually operable air-pressure regulator 238, the valve ports 0 and F, pipe 259;, to the 7 third air-operated receiver 21-0. Manual movement of regulator 238 causes consequent movement of second receiver llll which moves diff'er-entiaI "lever 2T2, mechanical linkage 274, and

difiere'ntial lever 315 to move napper in-2 1150 7 as to adjust the flapper 254 relative to the ='noz- Zle 263'. The flow of air through -noz"zle f2li3,--a's controlled-by flapper 266, controls the motor 265 -0f the third pilot or-relay valve 259. Whnth'e set point ct-the primar controller 2 56 is thus adjusted to a suitable position, the secondary cdntroner m can be connected so that its-set point is under the control of the primary controller 255. Then step 5 is taken by turning the switching valve 233 into the position in which it is shown in Fig. 11, step 5. In this position, mo tor 204 is connected through valve ports and a under the contra of the second pilot or relay This figure disclosesan air-operated controller for manually or automatically operating from a control location a motor-driven final control element positioned at a place remote from the corn trollocation. This controller comprises afiltered air supply 383 by means of which air at a suitable pressure is supplied to a first manually operable air pressure regulator 30! at the control location. From regulator 30!, a pipe 302 leads to a switching valve 303. Switching valve 333 is shown Figs. 12 and '13 diagrammatically. This valve may have various physical embodiments but the preferred embodiment consists of a tubular or cylindrical casing having eight ports or openings through it. These ports or openings are desig- :n'ated. by the reference characters H, J, N, O, P. On this casing is rotatably mounted a plug having openings through it connecting the various ports. From port L, a pipe 304 leads to motor 305, such as an air-operated diaphragm motor, for final control element 306. branch pipe 301 leads from pipe 334 to a Bourdon tube 388 or similar pressure-responsive device which operates a first air-pressure-operated indicator consisting of a pointer 30}! movable over a scale 3"].

A second manually operable air pressure 1 egu+ later 3 is also connected to the filtered 'ai r source 300. A pipe 312 connects the output side of the second regulator '3 to the port J of the switching valve 303. A pipe 313 connects theport O of the switching valve 303 to a pair of relatively movame parts such as an air-tight casingand a cooperating flexible bellows; constitutin a first air-operated receiver 3M. A nozz'le 315 i trolled by a flapper valve 315. Adi'iie'rentia' age .3'l1-inc1udins-a movable pivot is in mechanical linkage 318 'srtomsaic first re 3 l4 so as to adjust the-flapper valve '3 It. 'A pilot valvet3l 9 is operated by an air-operated motor I =33l com" en ance-with is nates'at the nozzle 315. an

outlet pipe 323 {f m pilot-valve "319 leads to port of relatively movable elements 335 such as i n ra-itig-htcasing and a cooperating flexible be1- lows. This seocndpair-of relatively movable elements constitutes an air-operated reset device ior'ming :p'art o"f an air-operated transmitter. This transmitter includes a second nozzle 33! eontroll'ed by as'econclfiapper valve 333. Flapper valve 332 isdoperate'd measuring element 328 and 'is-res'et biy elements33ll by means of a me- 'chanica'l linkage 333. The transmitter also includes a-sec'on'd zpil'otzv'alve 334 supplied with air .trom a source 335 of filtere'd air pressure which passes through gauge 336. A pipe 331. contains a restriction 338 and branches into pipe 339 which .termin'ateszin rnozzle'33-l and pipe 340 which communicates with an aireoperated motor 34! comprised of an air-tight casing and a cooperating flexible bellows A pipe 34-2 leads off from the second pilot valve .334. Air is supplied to the reset device 339 'from pip'ei342 through a pipe 343.

From tport :N of switching valve 303, a pipe 3% leads to. a ithird pair of relatively movable elementslconstitutingra second air-operated receiver 3.45. A mechanical linkage'343 connectsthe receiver 34-5 with one rend-"of the difierential 3! I so that movement'szof the second receiver 345 are .transmitted-;through differential 3|! to the first rfiapper valve 3H3. At the control location there isprovided'arecorder, generally indicated at 34?, and having a third p'air of'relatively movable eleinents sconstituting athird' air operated receiver i348 communicatingwith the second pilot or relay lval've 334 throughlp'ipes 342 and 349. A mechanical"linkage BSD-drives 5a pen arm 351 from the :third receiver. 343 so that :the pen arm marks a chart*352 in :the recorder 341.

x ilh'ere is also provided ;.a primary controller, generally indicated .at 353,-andl1aving a second measuring.element354 and a manually operable inde'x-setting knob '355 connected to a differential linkage z356wwhich drives-a third flapper valve .35-ltcontrolling the iiowof airthrough a third no'zzle:3'58 whichcontrols anair-power motor 359 forming fthejoperating mechanism for a third pilot valve .360 which constitutes a second transmitter. hrsource of-filtereduair 36I supplies air at fullpre'ssureato the nozzle 362 of .the third pilot valves-3 :andzalso supplies air through a restriction3613: at .a reduced pressure to nozzle 358 and motor, 59; A ipipe iili l connects the output side of-the third pilotj'valve 3'6B with port K ofswitch- -;i-ng-,valve; 30.3.

'j fiperationpf '12 hart-L so first manually operable pressure regulator I, pipe 362, ports Hand L, and pipe 304 to motor 305. Branch pipe 301 also conducts this air to Bourdon tube or spiral 308 so that the first airpressure-operated indicator indicates by means of pointer 309 and scale 3I0 the pressure'which is applied to motor 305 and consequently to the final control element 306. At the same time the control point of the controller 321 is observed on the recorder 34? just above the indicator 303-3 I 0. Inorder to prepare the controller to automatically control the final control'element 306 from the measuring element 328, the set point or air pressure sent out from pilot or relay valve 3I9- must be adjusted so that it is substantially equalto that currently applied to motor 305. If the pressure to be applied to the motor 305 should be different from that being applied, the process controlled'by the final control element 306 would be d sturbed. Consequently, the second step, shown in Fig; 13, step 2, comprises turning switching valve 303 into such a position that ports H and L remain connected while ports J and O are connected by a different connection separate from that connecting ports H and L. Air flows from source 300 through the second manually operable air pressure regulator 3 II pipe 3 I 2, ports J and O, pipe 3I3, to the first air-operated receiver 3I4. Any movement of the receiver 3I4 operates-the mechanical linkage 3I8 and the differential 3!? so as to adjust flapper 3 I6 relative to nozzle 3I5. Adjustment of flapper 3| 6 and the consequent variation of pressure at the nozzle 3I5 operates motor 320 and causes the output air pressure of the pilot valve or relay 3I9to vary correspondingly. The'output-pressure from pilot valve 3L9 is transmitted through pipes 323 and 324 to Bourdon tube or spiral 325 and causes the second airpressure-operated indicator. to indicate the pressure put out by pilot valve 3I9. Thisindication is given by pointer 326 which moves over scale 3H3 out of the path of movement of pointer 339. When the pressure measured by the first indicator 303 is equal to that measured by the second indicator 326 these pointers coincide and ind cate equal pressures by reference to scale 3I0. When these two pressures are equal, the switching valve 303 can be turned into the position shown in Fig. 13, step 3. In this position there is a connection between ports J and'O and there is another connection between ports P and L separate and distinct from that between ports J and 0. Manual operation of the second manual regulator 3i I causes positioning of final control element 306 because the second manual regulator 3I I forms a pneumatic transmitter whose movements are repeated by the first pneumatic receiver 3I4 which, in turn, transmits these movements by linkage 323 and differential 3II tofiapper 3H}. These corresponding movements of flapper 3I6 control the flow of air through nozzle 3I5 and consequently govern the output 'ofair from relay '3I9. The output air fromrelay 3I9' is conducted by ppe 323, through ports P and L, and'pip'e 304 to motor 365. To place the final control element 335 under the control of measuring element 328, the switching valve 303 is. turned. intothe position in which it is shown inFig. 13, step 4. In the step 4 position, there'is' an open communication between portsM and N and a second, separate open connection between ports P and L. The movements of measur ng element 328 in response to any variations of the condition measured by it, moves flapper 332 and thus varies the air flow through nozzle 33 I Conseduiehtlmmotor 34I op- 1'6 erates-relay-334 so that the output air from relay 334 is transmitted through pipe 342, ports M and N, and pipe 344 to the second air-operated receiver 345. The resulting movements of receiver 345 move linkage 346, differential 3 I I, and flapper 3 I6. Flapper 3I6 controls the flow of air through nozzle 3 I 5 and consequently the operations of motor 320 which cause corresponding movements of relay 3| 3. The output air from relay 3I9 is conducted through pipe 323, ports P and L, pipe 304 to motor 305. During this step a record of the movements of measuring element 323 is made on recorder 34! because any variation in the pressure in pipe 342 is transmitted through pipe 349 to the third air-operated receiver348 and causes movements of pen 35I by'means of linkage 350.

When it is desired to operate the final control element 306 automatically in response to the varia tions sensed by measuring element 354 of controller 353, switching valve 303 is turned into the position in which it is shown in Fig. 13, step 5. In the step 5 position, there is an open communication between ports K and N and a separate and distinct open connection between ports P and L.

Any variations in the condition to which measuring element 354 is responsive cause corresponding movements of measuring element 354. Movement of measuring element 354 moves differential 353 and flapper 351 relative to nozzle 358. Variations in the air flow through nozzle 358 cause the air-operated motor 359 to operate pilot valve or relay 360-whose outlet air is conducted through pipe 364, ports K and N, to the second airoperated receiver 345. Any movements of the second air-operated receiver 345 cause corresponding movements of the final control element 338 by means of the circuit already described.

-While in accordance with the provisions of the statutes, I have illustrated and described the best form of the invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention as set forth in the appended claims, and that in some cases certain features of the invention may sometimes be used to advantage without a corresponding use of other features.

Having now described my invention what I claim as new and desire to secure by Letters Patent is as follows:

1. In an air-operated controller for manually or automatically operating from a, control location a motor-driven final control element positioned at a remote location, the combination including, a first manually operable air-pressure regulator at the control location, a switching valve having a connection for connecting said first manual regulator to the motor of the final control element, an air-pressure-operated indicator-positioned atthe control location and connected to the motor of the final control element, a secondmanually operable-air-pressure regulator positioned at the control location, a pair of relatively movable parts constituting an air-operated receiver, said switching valve having connections for connecting said second manual regulator to said receiver, a nozzle, a flapper valve controlling the flow of air through said nozzle, a-measuring element,-a differentiallinkage including a movable pivot and connecting said measuring element to said flapper and connectingsaidreceiver-to said flapper so as to locate the set point of said flapper, a pilot valve having a motor operated in response to the flow through said nozzle, said switching valve having connections "connecting the output side of said pilot valve the motor'oi final control element, a

second air-pressure-operated indicator connected to the output side of said pilot valve and to said last mentioned connections, a second pair of relatively movable elements constituting an air-operated repositioning device, a second nozzle, a second flapper valve controlling the fiow of air through second nozzle, .a second pilot valve "'tuting a transmitter and having a motor be in response to the fiow of air through second nozzle, a mechanical connection between said measuring element and said second flapper valve, a connection between the output side of said second pilot valve and said repositioning device, a linkage between said repositioning device and said second flapper valve, a third pair of relatively movable elements constituting a. second air-operated receiver, a connection between said second receiver and the output side of said second pilot valve,-a pen arm operated by said second receiver, a chart located at the control location adjacent said manually operated air-pressure regulators so as to receive a record from said pen arm, a third pair ofrelatively movable elements constituting a third air-operated receiver, said switching valve having connections connecting said second regulator to said third receiver, a second measuring element, a third nozzle, a third pilot valve having a motor operable in response to the flow through said third nozzle, a third flapper valve controlling the flow through said third nozzle, 9, second differential linkage including a movable pivot and connecting said second measuring element to said third flapper and connecting said third receiver to said third flapper so that movement of said third receiver adjusts the position of said movable pivot and, consequently the set point of said third flapper, a fourth pair of relatively movable elements constituting a third air-operated repositioning device, a fourth nozzle, a

fourth flapper valve controlling the flow through said fourth nozzle, a fourth pilot valve constituting a transmitter and having a motor operated in response to the fiow through said fourth nozzle, a connection between the output side of said fourth pilot valve and said third repositioning device, and a mechanical linkage between said third repositioning device and said fourth flapper valve whereby said fourth flapper valve is positioned by movement of said third repositioning device, a fifth pair of movable elements constituting a fourth air-operated receiver, a pen arm operated by said fourth receiver and cooperating with said chart to make markings thereon, said switching valve having connections for connecting the outlet side of said third pilot valve and said first receiver.

2. In an air-operated control system for manually or automatically adjusting from a control station the set point of a controller remote from said control station and adjacent the final control element of the system, the combination including, a first manually operable air-pressure regulator at the control station, a switching valve having a connection for connecting said first manual regulator to the motor of the final control element, a second manually-operable airpressure regulator at the control station, a controller having a measuring element and located remote from said control station and adjacent and controlling the motor of the final control element of the system, a pneumatic transmission system including said second manual regulator'als a transmitter and a receiver operated by this transmitter and located in said controller and adjusting the set point of the controller, a'

second air-operated transmission system having a transmitter located in said controller and op erated in response to the movements of the measuring element of said controller, an indicator at said control station forming the receiver of and operated by the transmitter of said second transmission system for indicatim at the control station the position of the measuring element of said controller, and said switching valve having a connection for disconnecting said first manual regulator from and for connecting said controller to the motorof the final control element of the system. I

3. In an air-operated control system for manually or automatically adjusting from 'a control station the set point of a controller remote from said controlv station and adjacent the final control element of the system, the combination including, a first manually-operable air-pressure regulator at the control station, a switching valve having a connection for connecting said first manual regulator to the motor of the final control element, a second manually-operable airpressure regulator at the control station, a controller having a measuring element and located remote from said control station and adjacent and controlling the motor of the final control element of the system, a pneumatic transmission system including said second manual regulator as a transmitter and a-receiver operated by this transmitter and located in said controller and connected to said controller so as to adjust the set point of the controller, a second air-operated transmission system having a transmitter located in said controller and operated in response to the movements of the measuring element of said controller, an indicator at said control station forming the receiver of and operated by the transmitter of said second transmission system for indicating at the control station the position of the measuring element of said controller, said switch valve having a connection for disconnecting said first manual regulator from and for connecting said controller to the motor of the final control element of the system, a second controller, a third air-operated transmission system having a transmitter operated by said second controller and having the same receiver as said first mentioned transmission system, and said switch valve having a connection for connecting the transmitter of said third transmission system to the receiver of said first mentioned transmission system.

4. In an air-operated control system for manually or automatically operating from a control station a motor-driven final control element of the system, said element being remote from the control station, the combination including, a first manually-operated air-pressure regulator atthe control station, a second manually-operated airpressure regulator at the control station, a measuring instrument remote from the control station and adjacent the final control element, a first air-operated transmission system having a transmitter movable in response to the movements of said measuring element and having a receiver, a controller having a pilot valve operated by said receiver, a second receiver operable in response to the movements of said second regulator to adjust the set point of said controller, and a switching valve having a connection for connecting said first manual regulator to or from 19 the motor of the final control element and having a second connection for connecting said pilot valve from or to the motor of the final control element conversely to the connections between said first manual regulator and the motor.

5. In a power-operated control system for manually or automatically adjusting from a control station a controller remote from said control station and adjacent the final control element of the system, the combination including, a first manually-operable regulator at the control station, a switching valve having a connection for connecting said first manual regulator to the motor of the final control element, a second manually-operable regulator at the control station, a controller having a measuring element and located remote from said control station and adjacent and controlling the motor of the final control element of the system, a power-operated transmission system including said second manual regulator as a transmitter and a receiver operated by this transmitter and located in and connected to said controller so as to adjust said controller, a second power-operated transmission system having a transmitter located in said controller and operated in response to the movements of said controller, an indicator at the control station forming the receiver of and operated by the transmitter of said second transmission system for indicating at the control station the position of said controller, and said switching valve having a connection for disconnecting the first manual regulator from and for connecting said controller to the motor of the final control element of the system.

6. In a power-operated control system for man ually or automatically adjusting from a control station a controller remote from said control station and adjacent the final control element of the system, the combination including, a first manually operable regulator at the control station, a switching valve having a connection for connecting said first manual regulator to the motor of the final control element, a second manually-operable regulator at the control station, a controller having a measuring element and located remote from said control station and adjacent and controlling the motor of the final control element of the system, a first transmission system including said second manual regulator as a transmitter and a first receiver operated by this first transmitter and located in and adjusting said controller, a second transmission system having a second transmitter located in said controller and operated in response to the movements of said controller, an indicator at said control station forming a receiver of and operated by said second transmitter for indicating at the control station the position of said controller, said switching valve having a connection for disconnecting said first manual regulator from and for connecting said controller to the motor of the final control element of the system, and a second controller having a measuring element, a third transmission system having a third transmitter operated by said second controller and having the same receiver as said first mentioned transmission system, and said switching valve having a connection for connecting said third transmitter to the receiver of said first mentioned transmission system.

LOUIS GESS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,205,930 Otto June 25, 1940 2,470,452 Ackley May 17, 1949 2,529,875 Howard Nov. 14, 1950 

